1. Field of the Invention
The invention relates to improvements in an internal combustion engine of the split type operable on less than all of its cylinders when the engine load is below a given value.
2. Description of the Prior Art
It is known and desirable to increase the efficiency of a multicylinder internal combustion engine by reducing the number of cylinders on which the engine operates under predetermined engine operating conditions, particularly conditions of low engine load. Control systems have already been proposed which disable a number of cylinders in a multicylinder internal combustion engine by suppressing the supply of fuel to certain cylinders or by preventing the operation of the intake and exhaust valves of selected cylinders. Under given engine load conditions, the disablement of some of the cylinders of the engine increases the load on the those remaining in operation and, as a result, the energy conversion efficiency is increased.
One difficulty with such split type internal combustion engines is that large torque variations occurs, in spite of the use of a flywheel for output torque smoothing, causing large vibrations on the engine and vehicle body during the disablement of some of the cylinders, particularly under low speed conditions such as idling conditions. This is stemmed mainly from the structure where the period of rotation of the crankshaft is elongated during the disablement of some of the cylinders.
The present invention provides an improved split type internal combustion engine which can minimize vibrations on engine and vehicle bodies which have been found under low speed conditions by maintaining the period of engine output torque uncharged between full and split engine modes of operation.